In vitro effect of fluoroquinolones against Mycobacterium tuberculosis isolates from Agra & Kanpur region of north India.

Background & Objective: Fluoroquinolones (FQs) are important drugs used for treatment of drug resistant tuberculosis and are also now being considered as first line drugs to shorten the duration of treatment of tuberculosis (TB). In order to find out useful FQs for treatment of tuberculosis, the comparative efficacy of five FQs, namely, ofloxacin (OFL), ciprofloxacin (CIP), sparfloxacin (SPX), gatifloxacin (GAT) and levofloxacin (LEVX) was studied against Mycobacterium tuberculosis (MTB) isolates obtained from both treated and untreated patients from Agra and Kanpur regions of north India.

Methods: A total of 162 MTB isolates [including 110 MTB isolates obtained from untreated patients (Cat-I) and 52 isolates from treated patients (Cat-II)] were tested for their susceptibilities to FQs using standard minimum inhibitory concentration (MIC) method on Löwenstein-Jensen medium.

Results: Keeping in view the therapeutically achievable drug levels, it was found that in Cat-I 97.2 per cent (107/110) isolates were sensitive to GAT, 89 per cent (98/110) to LEVX at 1 microg/ml whereas 92.7 per cent (102/110) isolates were inhibited by OFL at 2 microg/ml and 73.6 per cent (81/110) to SPX at 0.5 microg/ml. Only 63.6 per cent (70/110) isolates were found to be sensitive to CIP at 2 microg/ml which increased to 89 per cent (98/110) at 4 microg/ml (higher than achievable peak serum level). On the other hand, among 52 isolates for Cat-II, 37 (71.2%) were found to be sensitive to GAT and 33 (63.5%) to LEVX at 1 microg/ml concentration, 28 (53.8%) to SPX at 0.5 microg/ml whereas 33 (63.5%) and 24 (46.2%) isolates were found to be sensitive to OFL and CIP at 2 microg/ml, respectively.

Interpretation & Conclusion: It appears that GAT has higher activity against MTB isolates followed by OFL, LEVX and SPX whereas CIP showed the lowest activity. GAT was also found to be the most effective FQ against multi-drug resistant (MDR) isolates both from Cat-I and Cat-II patients. Thus, except CIP, other FQs showed potential to be included in the treatment regimens of tuberculosis including MDR-TB.